android中view的寬高測量

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一般的，view測量的方法：

 

@Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); final ImageView imageView = (ImageView) findViewById(R.id.imageview); int w = View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED); int h = View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED); imageView.measure(w, h); int height =imageView.getMeasuredHeight(); int width =imageView.getMeasuredWidth(); textView.append( +height+,+width); System.out.println(執行完畢..+System.currentTimeMillis()); } //------------------------------------------------方法一 int w = View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED); int h = View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED); imageView.measure(w, h); int height =imageView.getMeasuredHeight(); int width =imageView.getMeasuredWidth(); textView.append( +height+,+width); //-----------------------------------------------方法二 ViewTreeObserver vto = imageView.getViewTreeObserver(); vto.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() { public boolean onPreDraw() { int height = imageView.getMeasuredHeight(); int width = imageView.getMeasuredWidth(); textView.append( +height+,+width); return true; } }); //-----------------------------------------------方法三 ViewTreeObserver vto2 = imageView.getViewTreeObserver(); vto2.addOnGlobalLayoutListener(new OnGlobalLayoutListener() { @Override public void onGlobalLayout() { imageView.getViewTreeObserver().removeGlobalOnLayoutListener(this); textView.append( +imageView.getHeight()+,+imageView.getWidth()); } });

 

 

最近由於要做自定義view，需要測量view寬高，發現一個不錯的api：

View.MeasureSpec.makeMeasureSpec(int,int)

參數1是一個數值，基於該數值計算

參數2是一個mode，指測量的方式，mode如下：

它有三種模式：
①、UNSPECIFIED(未指定)，父元素部隊自元素施加任何束縛，子元素可以得到任意想要的大小；
②、EXACTLY(完全)，父元素決定自元素的確切大小，子元素將被限定在給定的邊界裡而忽略它本身大小；
③、AT_MOST(至多)，子元素至多達到指定大小的值。

 

具體使用如下:

 

		int w = View.MeasureSpec.makeMeasureSpec(SCREEN_W,View.MeasureSpec.AT_MOST); 
		int h = View.MeasureSpec.makeMeasureSpec(SCREEN_H/2,View.MeasureSpec.AT_MOST); 
		view.measure(w, h);
		LogUtil.showlog(w: + w + ,h: + h);

 

 

1. int w = View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);
2. int h = View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);
3. textView.measure(w, h);